1. Field of the Invention
The present invention relates generally to machine tools and more particularly to a machine tool with an automatic tool changer for exchanging tools between a rotary spindle and a storage magazine storing a plurality of tools.
2. Description of the Prior Art
Within a tool changer heretofore known, such as for example, the device disclosed within U.S. Pat. No. 3,704,510, a drive key and a key-way complemental thereto are respectively provided upon each of the tools and a rotary sppindle so as to transmit the rotation of the spindle to the tools. Prior to a tool exchange operation, the spindle is stopped at a predetermined angular position, and in this connection, the tools stored within a storage magazine are prevented from experiencing any angular deviation as a result of a respective engagement between the drive keys of the tools and the key slots formed upon the magazine.
However, within such a tool changer, it is necessary to form the drive keys, the key-way, and the key slots with a high degree of precision thereby resulting in the requirement that a highly accurate spindle stop mechanism must also be fabricated. In addition, if the tools should angularly deviate even slightly during the transfer operation being performed by the transfer arm, insertion of the tools into the spindle and the magazine becomes extremely difficult.
Another tool changer is also known within which a protrusion is provided both on the spindle and upon each of the tools for positive drive therebetween, as shown for example, within U.S. Pat. No. 3,791,022. This device can accomplish a tool change operation without stopping the spindle at a predetermined angular position and is not required to provide clamping means for each of the tools in order to maintain the proper orientation of the same upon the magazine. However, a preliminary detection operation is necessary in order to predetermine whether or not the protrusion of a tool, which will be inserted into the spindle, may interfere with that of the spindle and as a result, if interference is anticipated, the angular phase of the spindle has to be altered.